Methods and fluid compositions for depositing and removing filter cake in a well bore

Abstract

The current invention provides methods of using and drilling and servicing fluid compositions for depositing and removing filter cake from the walls of a well bore. The compositions make use of particulate solid bridging agent comprised of a salt of an organic acid. The bridging particles are dissolvable by a clean-up solution comprised of a mild solvent that is less corrosive than the conventional strong mineral acids used for this purpose.

1. A method of treating a well bore comprising:
 preparing a drilling or servicing fluid composition comprised of water and a bridging agent wherein the bridging agent is a salt of an organic acid that is substantially insoluble in the drilling or servicing fluid; 
 depositing the bridging agent as a filter cake along the walls of the well bore; and 
 contacting the filter cake with a clean-up solution comprising water and a solvent for a period of time sufficient to dissolve at least a portion of the bridging agent. 
 
   
   
     2. The method of  claim 1  wherein the filter cake is contacted with the clean-up solution for a period of time sufficient to remove the bridging agent from the walls of the well bore. 
   
   
     3. The method of  claim 1  wherein the water comprises at least one of the following: fresh water or salt water and is present in the drilling or servicing fluid composition in an amount in the range of from about 35% to about 97% by weight of the composition. 
   
   
     4. The method of  claim 1  wherein the bridging agent is substantially insoluble in the drilling or servicing fluid and is dissolvable by solvents that are not corrosive to metal surfaces and completion equipment. 
   
   
     5. The method of  claim 1  wherein the bridging agent comprises at least one of the following: magnesium citrate, calcium citrate, calcium succinate, calcium malate, calcium tartrate, magnesium tartrate, bismuth citrate, or hydrates thereof. 
   
   
     6. The method of  claim 1  wherein the bridging agent is present in the drilling or servicing fluid composition in an amount in the range of from about 3% to about 40% by weight of the composition. 
   
   
     7. The method of  claim 1  wherein the bridging agent particle size ranges from about 1 to about 600 microns. 
   
   
     8. The method of  claim 1  wherein the bridging agent has a specific gravity of less than about 2.2. 
   
   
     9. The method of  claim 4  wherein the solvent comprises at least one of the following: organic acids, organic esters, organic salts, ammonium salts, or mixtures thereof. 
   
   
     10. The method of  claim 4  wherein the solvent comprises at least one of the following: salts or esters of ethylenediaminetetraacetic acid, salts or esters of nitrilotriacetic acid, citric acid, salts or esters of citric acid, salts or esters of diglycolic acid, succinic acid, ammonium salts, or mixtures thereof. 
   
   
     11. The method of  claim 1  wherein the solvent is present in the clean-up solution in an amount in the range of from about 2% to about 20% by weight of the clean-up solution. 
   
   
     12. A method of treating a well bore and separating drill solids from the drilling or servicing fluid and bridging agent particles comprising:
 preparing a drilling or servicing fluid comprised of water and a bridging agent wherein the bridging agent is a solid particulate salt of an organic acid; 
 depositing the bridging agent as a filter cake along the walls of the well bore; 
 separating and removing drill solids from the drilling or servicing fluid containing bridging agent; and 
 contacting the filter cake with a clean-up solution comprised of water and a solvent for a period of time such that the bridging agent is at least partially dissolved thereby. 
 
   
   
     13. The method of  claim 12  wherein the bridging agent particles have a specific gravity of less than about 2.2. 
   
   
     14. The method of  claim 12  whereby conventional rig separation equipment is utilized to separate the bridging agent particles from the drill solids. 
   
   
     15. The method of  claim 12  wherein the bridging agent is substantially insoluble in the drilling or servicing fluid and is dissolvable by solvents that are not corrosive to metal surfaces and completion equipment. 
   
   
     16. The method of  claim 12  wherein the bridging agent comprises at least one of the following: magnesium citrate, calcium citrate, calcium succinate, calcium malate, calcium tartrate, magnesium tartrate, bismuth citrate, or hydrates thereof. 
   
   
     17. The method of  claim 12  wherein the bridging agent is present in the drilling or servicing fluid composition in an amount in the range of from about 3% to about 40% by weight of the composition. 
   
   
     18. The method of  claim 12  wherein the bridging agent particle size ranges from about 1 to about 600 microns. 
   
   
     19. The method of  claim 12  wherein the solvent comprises at least one of the following: organic acids, organic esters, organic salts, ammonium salts, or mixtures thereof. 
   
   
     20. The method of  claim 12  wherein the solvent comprises at least one of the following: salts or esters of ethylenediaminetetraacetic acid, salts or esters of nitrilotriacetic acid, citric acid, salts or esters of citric acid, salts or esters of diglycolic acid, succinic acid, ammonium salts, or mixtures thereof.